Munching moths threaten state's trees

Sunday

Jul 27, 2014 at 6:00 AM

By Alex Ruppenthal

aruppenthal@wickedlocal.comKen Gooch, supervisor of the DCR Forest Health Program, sits in a small plane and looks down. Spread below him are the coastlines, hills and forests of the North Shore.To the untrained eye, itís beautiful. But thatís not what Gooch notices."I can see pockets of dead trees," Gooch said. "This has been probably some of the worst that Iíve seen."In the last year, Gooch has mapped 16,596 acres of defoliation across the state. And just about all of it caused by one particular insect ó the winter moth.Since landing in Massachusetts about 20 years ago, winter moths have chewed their way through trees in the eastern part of the state; Gooch said Gloucester and Rockport have suffered most. Last winter, the Department of Agricultural Resources received 800 reports of moths.And to address the invasion, foresters, gardeners and scientists are trying everything ó even enlisting other insects in the fight.A growing problemThe winter moth arrived on Cape Cod in the late 1990s, a side effect of the high volume of trade with Europe, where a variety of predators and parasites keep the moth in check.A member of the family operophtera, winter moths are most active in the winter, flying around the skies of the North Shore in November and December. They lay their eggs on trees ó many types of trees are the victims ó and the eggs hatch in April and May.The inch-long green caterpillars burrow into the buds of growing leaves. A single tree can harbor up to 250,000 caterpillars.The tree, rather than gaining energy through its leaves, expends energy trying to replace them. If three of these defoliation cycles happen in a row, the trees can die.In addition, the caterpillars themselves constitute a health menace, said Jennifer Forman Orth, head of the Massachusetts Introduced Pests Outreach Program."When the leaves open up, the caterpillars all drop down on these silken threads and they get all over your fence and car and whatever plant they land on, theyíll pretty much eat," Forman Orth said. "When the caterpillars are feeding in areas where the infestation is very high, it sounds like rain, but itís frass ó basically caterpillar poop."Gooch said the areas he is mapping show evidence of spreading defoliation. Heís sighted defoliation as far away as Connecticut and Rhode Island, along with the New Hampshire coast.Massachusetts is also receiving reports of the moths in central parts of the state."We made predictions ahead of time, we kind of knew it was going to be heavy on the North Shore," Gooch said. "There was a really heavy winter moth flight last winter."That heavy flight, plus the insulation of a heavy winter snowfall, could contribute to another big year in 2014.Thatís the concern of Medford Tree Warden Aggie Tuden, who said 80 percent of Norway maples in that city experienced some level of defoliation from winter moths this year. She keeps a notebook where she records sightings of the moths."Once they hit, they pretty much come back to the same trees, and then they increase their range over time," she said. "Every tree is a target, a potential target. The conditions were such that a large population survived the winter, so thatís why we had so much tree damage this spring."What can cities do to ward off the moths? Not much."There is no proven way to treat them," Tuden said.Weird scienceBut that might be changing.A team of professors from UMass and UConn declared the winter moth an invasive species in 2003. Joseph Elkinton, a UMass-Amherst entomologist, was part of that team, and now heís the stateís best hope of saving trees from the moths.Along with his team at UMass-Amherst, Elkinton is cultivating a population of cyzenis albicans, a fly native to Europe that preys exclusively on winter moth caterpillars.Over the past few years, Elkinton has released thousands of the flies in a handful of communities in Eastern Massachusetts, including Falmouth, Yarmouth, Wenham, Newton and Wellesley, where he said the flies have been particularly effective."This year, we have more flies to release than ever before," Elkinton said. "Iím confident weíre going to begin to fix this problem over the next five years."How do the flies work? The details are rather gruesome.Elkinton said the flies lay eggs on the surface of leaves. When caterpillars eat the eggs, the eggs hatch and the fly eats the caterpillar from inside."The beauty of the fly is, itís absolutely a winter moths specialist," Elkinton said. "When the winter moth density declines, the fly density declines with it. People donít notice the flies because it spends its time looking for winter moths."Elkintonís team, which includes about 20 graduate students, transports the flies from Vancouver. They then release the flies by the thousands; Elkinton said the team has released flies in 11 locations, including North Andover, Rockport and Boxford.Funding for the operation comes mostly from the U.S. Forest Service, which had to cut funding for the project by 15 to 20 percent during the past two years because of the federal sequester.The cost of the program is about $180,000 per year.Elkinton hopes the effectiveness of the flies helps maintain steady funding."We are on the verge of success," he said. "In the town of Wellesley, we established the fly all across the town and have seen high levels of parasitism approaching levels in Nova Scotia. I think we are on the verge of pricking the bubble."Gooch knows that stopping the moths rests on the wings of Elkinton, or rather, his flies."Thatís our best hope right now, is getting [the flies] established," said Gooch, whose research helps Elkinton select locations to release his flies.In the meantime, gardeners and foresters are attempting to control the moths using traditional means until the fly populations take hold. An insecticide called spinosad has had some success killing the caterpillars and gardening specialists recommend horticultural oils and mulching.But Gooch, who sees the mothsí destruction by the acre from above, said stopping the moths would take time ó and thatís a resource some worry is running out."They had a 20-year head start, and weíre trying to catch up," he said. "Itís going to be a long process. Itís definitely going to get worse before it gets better."